The ability of adult wild Atlantic spotted dolphins (Stenella frontalis) to synchronize vocalizations and behaviors has been found to be a key factor in overcoming much larger bottlenose dolphins during interspecies aggression (Cusick & Herzing, 2014). Furthermore, an adult baseline of behaviors and vocalizations during aggressive events containing synchrony has been established (Myers, Herzing, & Bjorklund, 2017). The present study examines juvenile aggression that contains bouts of synchrony to look at the development of this valuable skill. Differences of duration between adult and juvenile synchronous bouts, lag sequential analyses, frequencies of behavioral classes depending on the age class of the aggressor-recipient dynamic, differences in the frequencies of behavioral classes depending on the synchronous state and aggressorrecipient dynamic, and differences in behavioral classes exhibited by adults and juveniles during different synchronous states were analyzed. Adults, across group size, were able to maintain physical synchrony for a longer duration. Juveniles were often in loose synchronous groups before forming into a tight synchronous group as seen in adult synchrony. Vocal synchrony during adult aggression in terms of synchronized squawks were longer in duration than vocal synchrony during juvenile aggression. Juveniles used more pursuit behaviors during aggression, which indicates practice of a behavior that was found to be the most frequently used in interspecies aggression (Volker, 2016). Additionally, when adults were present in juvenile aggression, they used fewer aggressive behavioral classes demonstrating self-handicapping based on their opponent. This illustrates that there is a learning period for both vocal and physical synchrony for juvenile dolphins and that juvenile aggression, or play-fighting, is an important aspect of the development of these skills. This study is the first to describe juvenile synchrony in a population of wild Atlantic spotted dolphins. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection

Thesis (Ph. D.)--University of Hong Kong, 1999. / Includes bibliographical references (leaves 165-[202]).

Thesis (M.S.)--University of North Carolina Wilmington, 2007. / Includes bibliographical references (leaves: 64-66)

Seasonality of reproduction in common dolphins (Delphinus delphis), bottlenosed dolphins (Tursiops aduncus), striped dolphins (Stenella coeruleoalba) and humpbacked dolphins (Sousa chinensis) was examined using standard light microscope techniques. In the males four stages of testicular development could be identified. Individuals less than 2.26m in length and 105kg in mass had testes that contained small seminiferous tubules (0.048mm ± O.Olmm in diameter) and were classified either as juveniles (gonocytes present) or inactive (no gonocytes). Adults whose testes contained spermatozoa were said to be in late spermatogenesis while those whose testes contained no spermatids or spermatozoa were referred to as being in early spermatogenesis. In the males of D. delphis, T. aduncus and S. chinensis, late spermatogenesis occurred throughout the year and there was no significant difference in the monthly mean seminiferous tubule diameters (p > 0.05) within species. I conclude therefore that in these three species spermatogenesis is aseasonal. No conclusions about seasonality of spermatogenesis could be made for S. coeruleoalba owing to the small sample size. Large Graafian follicles occurred in the ovaries of all four species in most months of the year. However, the presence of Graafian follicles can not be taken as an indication of timing of reproduction since they may be remnants of follicles that have not yet degenerated. In D. delphis, T. aduncus and S. coeruleoalba luteal bodies (corpora albicans or corpora lutea) occurred in most months of the year. Active corpora lutea will be present in all months, in some members of the population, since gestation is approximately 12 months. The sperm structure of D. delphis was examined by scanning electron microscopy. The sperm of D. delphis is essentially similar to that described for two other species of Cetacea (Physeter catodon and Tursiops aduncus), having an ellipsoidally shaped head and a short mid-piece with nine mitochondria. The sperm dimensions for D. delphis were head length, 4.4pm; head width, 2.0pm and mid-piece length, 2.4pm. An analysis of foetal age in D. delphis showed that the majority of the foetuses were conceived in January with birth occurring the following summer (December), suggesting that reproduction is seasonal. Neonates of T. aduncus were found throughout the year suggesting aseasonal reproduction. Foetal material was not available for S. coeruleoalba and S. chinensis. Seasonality of reproduction in the four species of dolphins studied has been discussed in relation to feeding, migration and worldwide distribution of the species.

Worldwide research of bottlenose dolphins (Tursiops truncatus) has led to varied definitions and terminology regarding ways to group dolphins for study and management. An understanding of the demographic history and population structure of bottlenose dolphins residing within the Indian River Lagoon Estuary System (IRLES), Florida, is needed to help define the IRLES dolphin population: ecotype, population, or community. Using mitochondrial DNA sequencing and microsatellite genotyping, this study detected: (1) genetic differentiation between estuarine and coastal individuals (FstmtDNA=0.414, Fstmsat=0.057; p<0.05; K=2), (2) genetic differentiation between the Indian River Lagoon (IRL) and Mosquito Lagoon (ML) (FstmtDNA=0.0201, Fstmsat=0.0234; p<0.09), and (3) minute undefined sub-structure within the IRLES (FstmtDNA=-0.00 -0.0379, Fstmsat=0.00 - vii 0.0445; p>0.1). Additionally, within ML this study detected non-mixing cohabitation of two potential ecotypes, estuarine and coastal. These findings raise many questions regarding how dolphins are presently categorized and managed which are critical to population assessments including abundance, vital rates, and health. / by Sarah E. Rodgers. / Thesis (M.S.)--Florida Atlantic University, 2013. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.

Odontocetes use echolocation to detect, track, and discriminate their prey, as well as negotiate their environment. Their hearing abilities match the frequency of greatest sensitivity to the higher frequencies used for foraging and navigation. Hearing and echolocation together provide odontocetes with a highly developed biosonar system. This dissertation examines the hearing ability of several odontocete species to understand what signals they can perceive during echolocation. The variability in hearing ranges between species is examined in the context of phylogenetic and ecological differences among taxa. An autonomous hydrophone array is also developed that could be used in an expanded form in field deployments to study echolocation signals in a wider range of species. Methods for measuring hearing sensitivity include both psychophysical and electrophysiological procedures. Behavioral methods require a large time commitment, for both training and data collection, and can only be performed on captive dolphins. Auditory evoked potential (AEP) methods are non-invasive, rapid measurements of the brain's response to sound stimuli and allow for audiograms to be collected on stranded, high risk dolphins. By determining the hearing abilities of odontocetes either in captivity or during stranding, data can be collected about inter- and intraspecies variability, and the occurrence of hearing impairment. It can also be used as another diagnostic tool to determine the releasability of a stranded animal. A juvenile male short-finned pilot whale (Globicephala macrorhynchus) that stranded in Curacao had severe hearing impairment at all frequencies tested. Four female short-finned pilot whales tested had the best sensitivity at 40 kHz. The juveniles had greater high frequency sensitivity than the adult pilot whales. Cutoff frequencies were between 80 and 120 kHz. Hearing sensitivity was determined for the two mother/calf pairs of Risso's dolphins (Grampus griseus) before and after antibiotic treatment in order to measure any potential effects of antibiotic treatment. Greatest sensitivity occurred at 40 kHz and cutoff frequencies were around 120 kHz for all dolphins tested. Changes in hearing sensitivity after antibiotic dosage were 12 dB or less in all cases except one. The adult female Betty showed a threshold shift at 120 kHz of 54 dB from May to June, which partially demonstrates the presence of an ototoxic effect at one frequency. Dosages of antibiotics during drug treatment detailed in this study should be considered safe dosages of antibiotics for Risso's dolphins. AEP and behavioral methods were used to collect audiograms for three Stenella spp. dolphins. The frequency of best hearing for the Atlantic spotted dolphin and the spinner dolphin was 40 kHz, and their upper cutoff frequencies were above 120 kHz. The pantropical spotted dolphin had the greatest sensitivity at 10 kHz, and had severe high frequency hearing loss with a cutoff frequency between 14 and 20 kHz. Comparisons of high frequency hearing sensitivities among the species tested show two distinct groups. Short-finned pilot whales and Risso's dolphins have a cutoff frequency below 120 kHz, whereas Stenella spp. dolphins have cutoff frequencies above 120 kHz. Expanding the comparison to include other species, killer whales, pygmy killer whales, false killer whales, and long-finned pilot whales also have cutoff frequencies below 120 kHz. Common bottlenose dolphins, white-beaked dolphins, Indo-Pacific humpback dolphins, rough-toothed dolphins, and common dolphins have cutoff frequencies above 120 kHz. Genetic evidence exists for two subfamilies within Delphinidae (Vilstrup et al., 2011) and those species with cutoff frequencies below 120 kHz belong to the subfamily Globicephalinae and those species with cutoff frequencies above 120 kHz belong to the subfamily Delphininae. An autonomous, field-deployable hydrophone array was developed to measure free-swimming echolocation. The array contained 25 hydrophones, two cameras, and a synchronization unit on a PVC frame. The distinct click train was used to time-align all 25 channels, and the light was used to synchronize the video and acoustic recordings. Echolocation beam patterns were calculated and preliminary evidence shows a free-swimming dolphin utilizes head movement, beam steering and beam focusing. Among all areas of cetacean biology more research is necessary to gain a clearer picture of how odontocetes have adapted to function in their acoustic environment. The array system developed can be used to study how dolphins use echolocation in the wild, the impacts of anthropogenic sound on echolocation production, and the potential consequences of high frequency hearing loss.

published_or_final_version / Biological Sciences / Doctoral / Doctor of Philosophy

Graduation date: 1998

In Kaikoura, New Zealand dusky dolphins (Lagenorhynchus obscurus) are economically and ecologically important. However, more information on key habitat requirements is needed to develop an effective management plan for them. I use systematic shore-based observations and tour operator gathered boat-based observations and review night-time foraging observations to explore dusky dolphin occurrence and movement patterns. I discuss possible influence of prey on these patterns. From January to December 2006, I conducted crepuscular observations from three clifftop stations. With these geospatial data I examined occurrence, mean speed, and linearity over seasonal, diel, and tidal temporal scales. From October 1995 to November 2006 tour guides recorded GPS locations for over 5,000 dusky dolphin groups, allowing me to examine seasonal occurrence patterns. For both datasets I quantified occurrence patterns relative to depth, distance from the Kaikoura Canyon, and distance from shore. I reviewed the three studies conducted on dusky night foraging behavior in Kaikoura. I explore the effects of seasonal and lunar-scale changes in night-time light levels on dusky dolphin foraging behavior. Duskies exhibited seasonal and diel, but not tidal occurrence and movement patterns. Dolphins were found farther offshore, in deeper water, and travelling faster in winter and approaching sunset. The areas of highest sightings density were associated with the Kaikoura Canyon, and shifted almost entirely into the canyon in winter and approaching sunset. Dolphins made sharper turns during summer. Dolphins were, on average, closer to the Kaikoura Canyon than to shore. Seasonal occurrence patterns described by tour operator data agreed with those described by geospatial data collected by shorebased observers. Duskies exhibited flexible foraging behavior and appeared to use both seasonal and lunar phase specific tactics. Night-time light levels appeared to influence dusky foraging behavior, possibly through changes in prey behavior. Prey availability and behavior patterns appeared to influence dusky occurrence and movement patterns. The dolphins' affinity for the Kaikoura Canyon may reflect a strategy to maximize access to prey.

Thesis (M.S.)--Naval Postgraduate School, 2002. / Thesis advisor(s): Thomas G. Muir, Steven R. Baker, Samuel H. Ridgway. Includes bibliographical references (p. 129-130). Also available online.